Conventional data encryption networks commonly encrypt a Personal Identification Number with a particular encryption key for transmission along with data messages, sequence numbers, and the like, from one location node in the data network to the next location or node in the network. There, the encrypted PIN is decrypted using the encryption key, and re-encrypted with another encryption key for transmission to the next node in the network, and so on to the final node destination in the network.
In addition, such conventional data encryption networks also develop a Message Authentication Codes in various ways, and then encrypt such MAC for transmission to the next node using a MAC-encryption key that is different from the encryption key used to encrypt the PIN. At such next node, the MAC is decrypted using the MAC encryption key and then re-encrypted using a new MAC-encryption key for transmission to the next node, and so on to the final destination node in the network.
Further, such conventional networks operate upon the PIN, MAC, data message, sequence number, and the like, received and decrypted at the final destination node to consummate a transaction, or not, and then communicate an ACKnowledgment or Non-ACKnowledgment message back to the originating node of the network. Such ACK or NACK codes may be encrypted and decrypted in the course of transmission node by node through the network back to the originating node to provide an indication there of the status of the intended transaction at the final destination node.
Conventional data encryption networks of this type are impeded from handling greater volumes of messages from end to end by the requirement for separately encrypting and decrypting the PIN and MAC codes at each node using different encryption/decryption keys for each, and by the requirement for encrypting/decrypting at least the ACK code at each node along the return path in the network.
In addition, such conventional data encryption networks are susceptible to unauthorized intrusion and compromise of the security and message authenticity from node to node because of the separated PIN and MAC encryption/decryption techniques involved. For example, the encrypted PIN is vulnerable to being "stripped" away from the associated MAC, message, sequence number, and the like, and to being appended to a different MAC, message, sequence number, and the like, for faithful transmission over the network. Further, the return acknowledgment code may be intercepted and readily converted to a non-acknowledgment code or simply be altered in transmission after the transaction was completed at the destination node. Such a return code condition could, for example, cause the user to suffer the debiting of his account and, at the same time, the denial of completion of a credit purchase at point-of-sale terminal or other originating node.